1. Field of the Invention
The present invention relates generally to photolithographic methods and materials employed within microelectronics fabrications. More particularly, the present invention relates to photolithographic methods and materials employed in attenuating standing wave photoexposures of photoresist layers formed upon reflective layers employed within microelectronics fabrications.
2. Description of the Related Art
Integrated circuit microelectronics fabrications are formed from semiconductor substrates within and upon whose surfaces are formed resistors, transistors, diodes and other electrical circuit elements. The electrical circuit elements are connected internally and externally to the semiconductor substrate upon which they are formed through patterned conductor layers which are separated by dielectric layers.
As integrated circuit microelectronics fabrication technology has advanced and integrated circuit microelectronics fabrication device dimensions have decreased, several novel effects have become more pronounced within the methods and materials through which are formed advanced integrated circuit microelectronics fabrications. In particular, within the photolithographic methods and materials through which are formed patterned layers and patterned structures within advanced integrated circuit microelectronics fabrications, a significant novel effect which has evolved is the standing wave photoexposure effect by which actinic photoexposure radiation employed in photoexposing photoresist layers formed upon reflective layers within advanced integrated circuit microelectronics fabrications is reflected back from those reflective layers and into those photoresist layers in a fashion through which there is provided an inhomogeneous standing wave photoexposure of those photoresist layers. A pair of schematic cross-sectional diagrams illustrating the results of progressive stages in forming a pair of inhomogeneously standing wave photoexposed patterned photoresist layers upon a reflective layer within an advanced integrated circuit microelectronics fabrication is shown in FIG. 1 and FIG. 2.
Shown in FIG. 1 is a substrate 10 having formed thereover a blanket reflective layer 12 which in turn has formed thereupon a blanket photoresist layer 14. As shown within FIG. 1, the blanket photoresist layer 14 is photoexposed through a photoexposure reticle 16 while employing an actinic photoexposure radiation beam 18, where portions of the actinic photoexposure radiation beam 18 within the blanket photoresist layer 14 are reflected back from the surface of the blanket reflective layer 12 and into the blanket photoresist layer 14, thus yielding a standing wave photoexposure within the blanket photoresist layer 14.
Shown in FIG. 2 is the results of developing the photoexposed blanket photoresist layer 14 as illustrated in FIG. 1. Shown in FIG. 2 is a pair of standing wave photoexposed patterned photoresist layers 14a and 14b formed upon the blanket reflective layer 12, where due to the standing wave photoexposure of the blanket photoresist layer 14 the standing wave photoexposed patterned photoresist layers 14a and 14b have irregularly formed sidewalls. As is understood by a person skilled in the art, although FIG. 1 and FIG. 2 illustrate the blanket photoresist layer 14 and the pair of standing wave photoexposed patterned photoresist layers 14a and 14b as implicitly formed from a positive photoresist material, photoresist layers analogous to the blanket photoresist layer 14 as shown in FIG. 1 and the standing wave photoexposed patterned photoresist layers 14a and 14b as illustrated in FIG. 2 may also be formed when employing a blanket photoresist layer formed from a negative photoresist material. Standing wave photoexposed patterned photoresist layers, such as the pair of standing wave photoexposed patterned photoresist layers 14a and 14b as illustrated in FIG. 2, are undesirable within advanced integrated circuit microelectronics fabrications since there is often formed when employing those standing wave photoexposed patterned photoresist layers patterned integrated circuit layers and patterned integrated circuit structures with compromised dimensional integrity.
It is thus towards the goal of providing photolithographic methods and materials through which there may be attenuated standing wave photoexposures of photoresist layers formed upon reflective layers within microelectronics fabrications that the present invention is generally directed.
Various methods and materials have been disclosed in the arts of microelectronics fabrications for providing novel optical structures within microelectronics fabrications or for addressing novel optical considerations within microelectronics fabrications. For example, Doorman, et al., in U.S. Pat. No. 4,849,080 discloses a method for manufacturing an optical stripline waveguide for non-reciprocal optical components within microelectronics fabrications. The method employs forming a surface lattice disordered waveguide strip material surrounded by an iron garnet cladding material, where the iron garnet cladding material has an index of refraction less than the index of refraction of the surface lattice disordered waveguide strip material.
In addition, Tsujita, in U.S. Pat. No. 5,547,813, discloses a method for forming within a microelectronics fabrication a fine photoresist pattern of high resolution while employing a contrast enhancement layer. The method employs a spacer layer of index of refraction 1.3 to 1.4 separating the contrast enhancement layer from a photoresist layer from which is formed the fine photoresist pattern, where the thicknesses of the contrast enhancement layer and the spacer layer are further co-specified.
Most pertinent to the present invention, however, is Lur et al., U.S. Pat. No. 5,580,701, who disclose a method for eliminating a standing wave effect when photoexposing a photoresist layer formed upon a reflective layer within a microelectronics fabrication. The method employs an anti-reflective interference stack layer interposed between the photoresist layer and the reflective layer, where the relative indices of refraction of the materials from which are formed the photoresist layer, the anti-reflective interference stack layer and the reflective layer are further co-specified.
Desirable in the art are additional photolithographic methods and materials through which inhomogeneous standing wave photoexposures of photoresist layers formed upon reflective layers within microelectronics fabrications, such as but not limited to integrated circuit microelectronics fabrications, may be attenuated. It is towards this goal that the present invention is more specifically directed.